The centres house many vulnerable children and the charity warned that many of them are regularly subjected to mistreatment, including the use of physical force by staff.

Figures published by the Ministry of Justice in January revealed that there were on average 111 incidents of physical restraint per month during 2011-12 in the centres.

In the same year, 68 restraint incidents resulted in injury.

The charity pointed out that the law requires children with credible allegations of mistreatment should have access to an effective and independent investigation.

But while children and adults detained in prisons have access to an independent complaints system, no such system exists for children in the secure training centres.

And prisons are also subject to Freedom of Information, but the secure training centres – run by G4S and Serco – are exempt.

The charity’s legal team wrote an open letter to Justice Secretary Chris Grayling, calling on him to confirm that he will begin plans to change the system, within a fixed-time frame, or face a judicial review.

It said that the current complaints procedure was “wholly inadequate” and “unfair, discriminatory and contrary to the protections afforded by the European Convention on Human Rights.”

It called on Mr Grayling to implement a complaints system for children in the centres “that is fit for purpose and includes an accessible right of appeal to an independent body.”

Howard League chief executive Frances Crook said: “These child jails for profit have existed for 20 years yet there has been no proper public scrutiny of what has happened to the billions of taxpayers’ money.

“We have to make sure children know they will be listened to by someone fair and impartial when things are going wrong if we are to change the culture of impunity, change poor practice and avoid children being seriously mistreated.”

…

Two children have died in secure training centres. Adam Rickwood, 14, took his own life at the Serco-run Hassockfield secure training centre in Co Durham in 2004 after being subjected to an unlawful use of force.

In the same year, Gareth Myatt, 15, died while being restrained by staff at the G4S-run Rainsbrook secure training centre in Northamptonshire.

Outsourcing, the exploitation of prisoners and my Twitter ruck with G4S: here.